1. Field of the Invention
The present invention relates to a cutter assembly and, more particularly, to a cutter assembly having a screw-locking device.
2. Description of Related Art
A retractable cutter is applied to cut paper or wooden sheets and substantially comprises a blade holder, a blade and a slider. The slider is mounted on the blade holder. The blade is mounted slidably in the blade holder and is connected to the slider. When the slider is pushed, the blade is moved relative to the blade holder to extend out of the blade holder to enable a user to cut an object by the cutter. To hold the blade at a desired position with a desired extension length relative to the blade holder and to provide a large positioning force, a screw-locking device is mounted on the slider for cutting a thick or hard object. The conventional screw-locking device substantially comprises a threaded rod mounted on the slider. When the threaded rod is rotated to make the threaded rod abut against an inner surface of the blade holder, the slider can be positioned relative to the blade holder. When the threaded rod is released, the slider is moveable relative to the blade holder to adjust the extension length of the blade relative to the blade holder.
However, the locking force of the conventional screw-locking device is achieved by friction between the end of the threaded rod and the inner surface of the blade holder. Thus, the locking force of the conventional screw-locking device is not sufficient, and the slider and the blade are easily moved when a specific pushing or pulling force is applied to the cutter. Thus, the blade cannot be positioned firmly and stably. In addition, the threaded rod and the inner surface of the blade holder are easily worn off due to the abutment between the threaded rod and the inner surface of the blade holder, and depressions or scratches are easily formed on the inner surface of the blade holder. Accordingly, the conventional screw-locking device cannot provide a sufficient locking force to the blade.
To overcome the shortcomings, the present invention provides a cutter assembly to mitigate or obviate the aforementioned problems.